The present inventors have previously proposed a six-axis force sensor disclosed in JP-A-2003-254843. In this six-axis force sensor, buffering devices are disposed about the periphery of the six-axis force sensor so as to reduce the magnitude of external force applied to the external force application portion (force-exerting unit) of the six-axis force sensor chip of the semiconductor substrate. The level of external force that can thereby be measured by the six-axis force sensor is dramatically increased, and the range of application can be expanded. Also, the six-axis force sensor can solve the problem of multiaxial interference even if the structure is provided with a buffering device.
A force/moment detector is disclosed in JP-A-1-75930 (Japanese Patent 2607096). In this force/moment detector, a total of 12 resistance elements are formed on a single crystal silicon substrate, as shown in FIG. 1 and other drawings in JP-A-1-75930, and a transducer for converting mechanical deformations into electric signals is included. In the force/moment detector described above, a first strain element and a second strain element are provided, the single crystal substrate is disposed on the first strain element, and the first and second strain elements are connected by an arm-like member.
In a force sensor such as the one described above, there are cases in which a semiconductor sensor chip is used in which semiconductor technology is used for the portion that senses force and moment. Since a semiconductor sensor chip uses a semiconductor substrate to form a portion that receives external force, there is a limit to the force that can be applied. When excessive force or moment is applied, the chip on the semiconductor substrate is liable to be damaged. In view of this situation, a buffering device is preferably provided. This device has an external force-dampening mechanism that weakens external force in order to protect the chip that constitutes the force sensor. When a force sensor is furthermore used, for example, in an external force application unit in an industrial robot or the like, an excessively large buffering device cannot be used due to installation space constraints. From the viewpoint of installation location, installation space, and other considerations related to the interior of a robot or other apparatus, there is a need to develop a buffering device for a force sensor modified in a variety of ways to have a more optimal form and structure.
There is therefore a need for a force sensor that can suitably moderate axial force applied to the force sensor chip and can be installed in an optimal shape or mounting state in accordance with the installation location, installable space, and other considerations.